The present invention relates to devices for injecting, delivering, infusing, dispensing or administering a substance, and to methods of making and using such devices. More particularly, it relates to a needle guard device which is or can be attached to an injection device of a type which may be used for administering or self-administering medicaments, for example insulin. The injection device may be a simple syringe or a syringe which is disposed of once it has been used. In such applications, the needle guard may be manufactured separately from the injection device and connected to the injection device in readiness for administering, or it may be an integrated part of the injection device and be disposed of with it. The injection device may be designed for repeated use and to enable a dose to be set or selected for the product to be administered. In some embodiments, the injection device may be an injection pen of the type used to treat diabetes and, these days, for other treatments as well.
When handling injection devices, there is a risk that patients or medical staff could be injured by an injection needle and/or be infected by an accidental stick by an injection needle that has already been used. With a view to preventing this, needle guard devices with a displaceable needle guard have been developed. For the injection, the injection device fitted with the needle guard device is pushed against the skin via the needle guard. Due to the pressure, the injection device, with the injection needle projecting from it in the distal (forward, front or injection) direction, moves in the distal direction relative to the needle guard so that the injection needle pierces the skin. Accordingly, the needle guard effects a movement in the proximal direction (rearwardly) relative to the injection device as far as a releasing position in which the injection needle projects in the distal direction beyond the needle guard by its injection portion which pierces the skin. When the injection needle is pulled back out of the skin, the needle guard is subjected to an elastic force of a rebounding element and moves in the distal direction again as far as a guard position in which it extends beyond the injection needle, including the needle tip. On reaching the guard position, the needle guard locks automatically so that it can not move back in the proximal direction relative to the injection needle again.
U.S. Pat. No. 6,773,415 B2 discloses such a needle guard device, which comprises an injection needle, a needle holder and a needle guard. The needle guard surrounds the needle holder and is mounted on it so that it can move axially. A locking element which is able to move axially is accommodated in the needle guard which is blocked on the needle holder when the needle guard is in the releasing position and is blocked on the needle guard when the injection needle is pulled out so that the needle guard is axially secured relative to the needle holder by the locking element after the injection. Since the locking element is blocked on both the needle holder and the needle guard and must also ensure a clean axial guiding action in sliding contact with the needle guard, it has a complex shape. The needle holder must also be of a specific shape to guide and hold the needle guard on the one hand and to lock the locking element axially on the other hand. The rebounding member must also be axially guided by the locking element and must therefore be relatively slim.
A needle guard device which can be attached to an injection device incorporating an injection needle is described in patent specification WO 01/91837 A1, for example. The device comprises a needle holder with an injection needle extending in the distal direction and a needle guard, which is mounted on the needle holder so that it can be moved out of a proximal position against the force of a return element into the releasing position and back out of the releasing position. The needle holder forms a branched guide track and the needle guard forms a locating element which is guided along the guide track. During an injection, the locating element moves through the two branches of the guide track one after the other and latches on the end of one branch of the guide track when the injection needle is pulled out so that the needle guard is blocked to prevent it from moving in the proximal direction again. This needle guard device also requires a needle holder with a complex shape. In addition, there is no guaranteeing that the catch connection defining the guard position will not be inadvertently released to the desired degree of reliability because the locating element is elastically bent several times before latching and may therefore project outwardly.